Rajala Pauliina, Bomberg Malin
Materials Performance, VTT Technical Research Centre of Finland Espoo, Finland.
Materials Performance, VTT Technical Research Centre of FinlandEspoo, Finland; Material Processing and Geotechnology, VTT Technical Research Centre of FinlandEspoo, Finland.
Front Microbiol. 2017 Mar 17;8:431. doi: 10.3389/fmicb.2017.00431. eCollection 2017.
Microbial communities in deep subsurface environments comprise a large portion of Earth's biomass, but the microbial activity in these habitats is largely unknown. Here, we studied how microorganisms from two isolated groundwater fractures at 180 and 500 m depths of the Outokumpu Deep Drillhole (Finland) responded to methane or methanol amendment, in the presence or absence of sulfate as an additional electron acceptor. Methane is a plausible intermediate in the deep subsurface carbon cycle, and electron acceptors such as sulfate are critical components for oxidation processes. In fact, the majority of the available carbon in the Outokumpu deep biosphere is present as methane. Methanol is an intermediate of methane oxidation, but may also be produced through degradation of organic matter. The fracture fluid samples were incubated with methane or methanol in the presence or absence of sulfate as electron acceptor. The metabolic response of microbial communities was measured by staining the microbial cells with fluorescent redox sensitive dye combined with flow cytometry, and DNA or cDNA-derived amplicon sequencing. The microbial community of the fracture zone at the 180 m depth was originally considerably more respiratory active and 10-fold more numerous (10 cells ml at 180 m depth and 10 cells ml at 500 m depth) than the community of the fracture zone at the 500 m. However, the dormant microbial community at the 500 m depth rapidly reactivated their transcription and respiration systems in the presence of methane or methanol, whereas in the shallower fracture zone only a small sub-population was able to utilize the newly available carbon source. In addition, the composition of substrate activated microbial communities differed at both depths from original microbial communities. The results demonstrate that OTUs representing minor groups of the total microbial communities play an important role when microbial communities face changes in environmental conditions.
地下深层环境中的微生物群落占地球生物量的很大一部分，但这些生境中的微生物活动在很大程度上尚不为人所知。在此，我们研究了来自芬兰奥托昆普深钻孔180米和500米深处两个孤立地下水裂隙中的微生物，在有或没有作为额外电子受体的硫酸盐存在的情况下，对甲烷或甲醇添加的反应。甲烷是地下深层碳循环中一种可能的中间产物，而诸如硫酸盐等电子受体是氧化过程的关键组成部分。事实上，奥托昆普深部生物圈中大部分可用碳以甲烷形式存在。甲醇是甲烷氧化的中间产物，但也可能通过有机物降解产生。将裂隙流体样本在有或没有作为电子受体的硫酸盐存在的情况下与甲烷或甲醇一起培养。通过用荧光氧化还原敏感染料对微生物细胞进行染色并结合流式细胞术，以及DNA或cDNA衍生的扩增子测序来测量微生物群落的代谢反应。180米深处裂隙带的微生物群落最初的呼吸活性明显更高，数量比500米深处裂隙带的群落多10倍（180米深处为10个细胞/毫升，500米深处为10个细胞/毫升）。然而，500米深处休眠的微生物群落在存在甲烷或甲醇的情况下迅速重新激活其转录和呼吸系统，而在较浅的裂隙带只有一小部分亚群能够利用新获得的碳源。此外，在两个深度处，底物激活的微生物群落组成与原始微生物群落不同。结果表明，当微生物群落面临环境条件变化时，代表总微生物群落中较小群体的操作分类单元发挥着重要作用。
